Hybrid electric vehicle drive apparatus

ABSTRACT

A hybrid electric vehicle drive apparatus has a setting portion for setting a limit value of a driving torque that a motor outputs when driving a hybrid electric vehicle by the power of the motor only, based on a maximum torque that the motor enables to output and a starting torque used to start an internal combustion engine by the motor. The setting portion sets the limit value to a first value and sets the limit value to a second value which is greater than the first value when a vehicle speed of the vehicle does not increase even though an accelerator pedal position degree increases while the vehicle is being driven only by the motor.

TECHNICAL FIELD

The present invention relates to a hybrid electric vehicle driveapparatus.

BACKGROUND ART

FIG. 10 is a schematic view showing the configuration of a power outputapparatus for a vehicle which is described in patent literature 1. Asshown in FIG. 10, the power output apparatus disclosed in PatentLiterature 1 includes an engine 6, a motor 7, a battery which supplieselectric power to the motor 7 (not shown), a first speed changingportion which is connected to the engine 6 via a first clutch 41 andwhich includes a third-speed gear pair 23, a fifth-speed gear pair 25and a first-speed shifter 51 and a second speed changing portion whichis connected to the engine 6 via a second clutch 42 and which includes asecond-speed gear pair 22, a fourth-speed gear pair 24 and asecond-speed shifter 52. The power of at least one of the engine 6 andthe motor 7 is inputted to the first speed changing portion, and thepower of the engine 6 is inputted into the second speed changingportion. The driving with the odd numbered speed gears and the EVdriving can be effected through the first speed changing portion, andthe driving with the even numbered speed gears can be effected throughthe second speed changing portion. The speed change can be effected bychanging the clutch engagement between the first clutch 41 and thesecond clutch 42. In the event that it is determined that the gradientof a road surface on which this vehicle is driven is equal to or greaterthan a threshold, a limit value of torque outputted by the motor 7 indriving the vehicle with the power of the motor 7 only is set as atorque limit value which is greater than a normal one within the scopeof a maximum torque. As a result, for example, when the vehicle isdriven in the EV driving mode on an ascending slope, the accelerationrequirement and the improved fuel economy can both be satisfied.

RELATED ART LITERATURE Patent Literature

-   Patent Literature 1: JP-A-2011-213166

SUMMARY OF THE INVENTION Problem that the Invention is to Solve

In the vehicle described above, the torque limit value of the motor 7 isset based only on the gradient of the road surface on which the vehicleis EV driven. In case the torque limit value is greater than the normalone, the motor 7 can output torque which satisfies the requiredacceleration. However, the motor 7 is driven by the electric powersupplied from the battery when the vehicle is EV driven, and therefore,the consumption of the battery increases as the output torque of themotor 7 increases. In this way, when the torque limit value which isgreater than the normal one is set based only on the gradient of theroad surface, the battery is consumed according not to the requirementof the driver but to the gradient of the driving path of the vehicle.

An object of the invention is to provide a hybrid electric vehicle driveapparatus which enables a control according to a requirement of a driverbased on behavior of the vehicle that are sensed by the driver.

Means for Solving the Problem

With a view to achieving the object by solving the problem, according toan invention claimed in claim 1, there is provided a hybrid electricvehicle drive apparatus including an internal combustion engine (forexample, an engine 6 in an embodiment which will be described later), atransmission (for example, a transmission 20 in the embodiment) havingtwo or more input shafts (for example, a first main shaft 11, a secondintermediate shaft 16 in the embodiment), an electric motor (forexample, a motor 7 in the embodiment) which is connected to either ofthe input shafts of the transmission so as to transmit power thereto,and an engaging and disengaging portion (for example, a first clutch 41,a second clutch 42 in the embodiment) which engages and disengages theinternal combustion engine and the transmission, and configured to bedriven by power of at least one of the internal combustion engine andthe electric motor, having:

a maximum torque deriving portion (for example, a maximum torquederiving portion 83 in the embodiment) for deriving a maximum torquewhich the electric motor enables to output;

a starting torque deriving portion (for example, a starting torquederiving portion 82 in the embodiment) for deriving a starting torquefor use in starting the internal combustion engine by the electricmotor;

a torque limit value setting portion (for example, a torque limit valuesetting portion 84 in the embodiment) for setting a limit value of adriving torque that the electric motor outputs when the vehicle driveswith power of the electric motor only, based on the maximum torque andthe starting torque;

a vehicle speed acquiring portion (for example, a vehicle speeddetermining portion 85 in the embodiment) for acquiring a speed of thevehicle; and

an accelerator pedal position degree acquiring portion (for example, anaccelerator pedal position degree determining portion 81) for acquiringa position degree of an accelerator pedal,

wherein the torque limit value setting portion sets the driving torquelimit value to a first driving torque value and sets the limit value ofthe driving torque to a second driving torque value which is greaterthan the first driving torque value when the speed does not increaseeven though the accelerator pedal position degree increases while thevehicle is being driven only by the electric motor.

Further, in the hybrid electric vehicle drive apparatus according to aninvention of claim 2, the torque limit value setting portion sets thelimit value of the driving torque to the second driving torque valuewhich is greater than the first driving torque value when the vehiclespeed does not continue to increase over a predetermined length of timeor more even though the accelerator pedal position degree increases.

Further, in the hybrid electric vehicle drive apparatus according to aninvention of claim 3, the torque limit value setting portion reduces thelimit value of the driving torque from the second driving torque valuein a case that the accelerator pedal position degree is lowered with thelimit value of the driving torque set to the second driving torquevalue.

Further, in the hybrid electric vehicle drive apparatus according to aninvention of claim 4, the torque limit value setting portion reduces thelimit value of the driving torque step by step as the accelerator pedalposition degree is lowered when the torque limit value setting portionreduces the limit value of the driving torque from the second drivingtorque value to the first driving torque value.

Further, in the hybrid electric vehicle drive apparatus according to aninvention of claim 5, when the vehicle speed is equal to or greater thana predetermined vehicle speed, the electric motor outputs the startingtorque in addition to the driving torque to start the internalcombustion engine.

Further, the hybrid electric vehicle drive apparatus according to aninvention of claim 6, the torque limit value setting portion sets thelimit value of the driving torque to the first driving torque valueafter the internal combustion engine is started.

Further, the hybrid electric vehicle drive apparatus according to aninvention of claim 7, a difference between the second driving torquevalue and the maximum torque is a minimum torque which is necessary forthe electric motor to start the internal combustion engine.

Advantage of the Invention

According to the hybrid electric vehicle drive apparatus according tothe inventions of claims 1 to 7, it is possible to realize the controlaccording to the requirement of the driver based on the actual behaviorof the vehicle that are sensed by the driver.

According to the hybrid electric vehicle drive apparatus of theinvention of claim 2, it is possible to prevent the consumption ofelectric power of the battery which would be caused by the frequentincrease of the torque limit value.

According the hybrid electric vehicle drive apparatus of the inventionof claim 3, it is possible to prevent the increase in torque limit valuewhich is equal to or more than required.

According to the hybrid electric vehicle drive apparatus of theinvention of claim 4, it is possible to prevent the driver from feelinga sensation of physical disorder which is triggered by the drasticchange in torque limit value.

According to the hybrid electric vehicle drive apparatus of theinvention of claim 5, it is possible to secure the driving force of thevehicle while suppressing the consumption of electric power of thebattery.

According to the hybrid electric vehicle drive apparatus of theinvention of claim 6, it is possible to suppress the consumption ofelectric power of the battery by the drive apparatus of the motorbecause the limit value of the driving torque is set to the first torquelimit value while the engine is being driven.

According to the hybrid electric vehicle drive apparatus of theinvention of claim 7, it is possible to secure the driving force of thevehicle by increasing the vehicle speed by the motor to start the enginebecause the minimum torque which is necessary to start the engine can besecured even in the event that the driving torque is increased to thesecond driving torque value.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram of a hybrid electric vehicle driveapparatus of the invention.

FIG. 2 is a block diagram of a control system of the hybrid electricvehicle drive apparatus shown in FIG. 1.

FIG. 3 is a block diagram of an ECU of the hybrid electric vehicle driveapparatus shown in FIG. 1.

FIGS. 4A and 4B show the hybrid electric vehicle drive apparatus in a1st EV driving mode, and FIG. 4A is a speed diagram thereof and FIG. 4Bis a diagram showing a torque transmission therein.

FIG. 5 is a graph showing a relationship between the driving force of amotor and an engine or the rotation speed of a crankshaft of the engineand the vehicle speed in each speed gear.

FIGS. 6A and 6B show the hybrid electric vehicle drive apparatus in a1st EV driving Pre2 mode, and FIG. 6A is a speed diagram thereof andFIG. 6B is a diagram showing a torque transmission therein.

FIGS. 7A and 7B show the hybrid electric vehicle drive apparatus in the1st EV driving mode with the engine started in a second speed gear, andFIG. 7A is a speed diagram thereof and FIG. 7B is a diagram showing atorque transmission therein.

FIG. 8 is a timing chart showing an example of a change in eachparameter during EV driving on an ascending path.

FIG. 9 is a graph showing a relationship between the vehicle speed and athreshold of a counter value.

FIG. 10 is a schematic diagram showing the configuration of a poweroutput apparatus in a vehicle disclosed in patent literature 1.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of a hybrid electric vehicle drive apparatusaccording to the invention will be described by reference to FIG. 1.

As shown in FIG. 1, a hybrid electric vehicle drive apparatus 1 of theembodiment drives driving wheels DW, DW (a driven portion) via driveshafts 9, 9 of a hybrid electric vehicle (not shown) and includes aninternal combustion engine (hereinafter, referred to as an “engine”) 6which is a drive source, an electric motor (hereinafter, referred to asa “motor”) 7 and a transmission 20 which transmits power to the drivingwheels DW, DW.

The engine 6 is, for example, a gasoline engine or a diesel engine, anda first clutch (a first engaging and disengaging portion) 41 and asecond clutch (a second engaging and disengaging portion) 42 of thetransmission 20 are provided on a crankshaft 6 a of the engine 6.

The motor 7 is a three-phase brushless DC motor and has a stator 71 madeup of 3n armatures 71 a and a rotor 72 which is disposed so as to facethe stator 71. The armatures 71 a are each made up of an iron core 71 band a coil 71 c which is wound around the iron core 71 b and are fixedto a casing, not shown, while being arranged at substantially equalintervals in a circumferential direction about a rotating shaft. 3ncoils 71 c make up n sets of three-phase coils of U phase, V phase and Wphase.

The rotor 72 has an iron core 72 a and n permanent magnets 72 b whichare arranged at substantially equal intervals about the rotating shaft,and the polarities of two adjacent permanent magnets 72 b are differentfrom each other. A fixing portion 72 c where the iron core 72 a is fixedhas a hollow circular cylindrical shape and is disposed on an outercircumferential side of an annulus of ring gear 35 of a planetary gearmechanism 30, which will be described later, so as to be connected to asun gear 32 of the planetary gear mechanism 30. By adopting thisconfiguration, the rotor 72 is made to rotate together with the sun gear32 of the planetary gear mechanism 30.

The planetary gear mechanism 30 has the sun gear 32, the ring gear 35which is disposed concentric with the sun gear 32 and which is alsodisposed so as to surround the sun gear 32, planetary gears 34 whichmesh with the sun gear 32 and the ring gear 35 and a planetary carrier36 which supports the planetary gears 34 so as to revolve on their ownaxes and to walk around the sun gear 32. In this way, the sun gear 32,the ring gear 35 and the carrier 36 are configured to perform freely adifferential action relative to one another.

A synchromesh mechanism 61 (a lock mechanism) is provided on the ringgear 35, and this synchromesh mechanism 61 has a synchronizing mechanism(a synchronizer mechanism) and is configured to slop the rotation of thering gear 35. A brake mechanism may be employed in place of thesynchromesh mechanism 61.

The transmission 20 is a so-called twin clutch type transmission andincludes the first clutch 41 and the second clutch 42, which have beendescribed before, the planetary gear mechanism 30, and a plurality ofspeed changing gear groups, which will be described later.

To describe this more specifically, the transmission 20 includes a firstprimary shaft 11 (a first input shaft) which is disposed coastal withthe crankshaft 6 a of the engine 6 (on a rotational axis A1), a secondprimary shaft 12, a connecting shaft 13, a counter shaft 14 (an outputshaft) which can rotate freely about a rotational axis B1 which isdisposed parallel to the rotational axis A1, a first intermediate shaft15 which can rotate freely about a rotational axis C1 which is disposedparallel to the rotational axis A1, a second intermediate shaft 16 (asecond input shaft) which can rotate freely about a rotational axis D1which is disposed parallel to the rotational axis A1, and a reverseshaft 17 which can rotate freely about a rotational axis E1 which isdisposed parallel to the rotational axis A1.

The first clutch 41 is provided on the first primary shaft 11 at a sidefacing the engine 6, and the sun gear 32 of the planetary gear mechanism30 and the rotor 72 of the motor 7 are mounted on the first primaryshaft 11 at an opposite side to the side facing the engine 6.Consequently, the first primary shaft 11 is selectively connected to thecrankshaft 6 a of the engine 6 by the first clutch 41 and is alsoconnected directly to the motor 7, so that the power of the engine 6and/or the motor 7 is transmitted to the sun gear 32.

The second primary shaft 12 is formed hollow and shorter than the firstprimary shaft 11 and is disposed so as to surround the circumference ofa portion of the first primary shaft 11 which lies on the side facingthe engine 6 while allowed to rotate freely relative to the firstprimary shaft 11. The second clutch 42 is provided on the second primaryshaft 12 at a side facing the engine 6, and an idler drive gear 27 a ismounted integrally on the second primary shaft 12 at an opposite side tothe side facing the engine 6. Consequently, the second primary shaft 12is selectively connected to the crankshaft 6 a of the engine 6 by thesecond clutch 42, so that the power of the engine 6 is transmitted tothe idler drive gear 27 a.

The connecting shaft 13 is formed hollow and shorter than the firstprimary shaft 11 and is disposed so as to surround the circumference ofa portion of the first primary shaft 11 which lies on the opposite sideto the side facing the engine 6 while allowed to rotate freely relativeto the first primary shaft 11. A third-speed drive gear 23 a is mountedintegrally on the connecting shaft 13 at a side facing the engine 6, andthe carrier 36 of the planetary gear mechanism 30 is mounted integrallyon the connecting shaft 13 at an opposite side to the side facing theengine 6. Consequently, the carrier 36 and the third-speed drive gear 23a which are mounted on the connecting shaft 13 rotate together by theplanetary gear 34 walking around the sun gear 32.

Further, a fifth-speed drive gear 25 a is provided on the first primaryshaft 11 so as to rotate relative to the first primary shaft 11, and areverse driven gear 28 b is mounted on the first primary shaft 11 so asto rotate together with the first primary shaft 11, both the fifth-speeddrive gear 25 a and the reverse driven gear 28 b being disposed betweenthe third-speed drive gear 23 a mounted on the connecting shaft 13 andthe idler drive gear 27 a mounted on the second primary shaft 12. Afirst speed changing shifter 51 is provided between the third-speeddrive gear 23 a and the fifth-speed drive gear 25 a so as to connect ordisconnect the first primary shaft 11 and the third-speed drive gear 23a or the fifth-speed drive gear 25 a. When the first speed changingshifter 51 is shifted in a third-speed connecting position, the firstprimary shaft 11 and the third-speed drive gear 23 a are connected torotate together. When the first speed changing shifter 51 is shifted ina fifth-speed connecting position, the first primary shaft 11 and thefifth-speed drive gear 25 a rotate together. When the first speedchanging shifter 51 is in a neutral position, the first primary shaft 11rotates relative to the third-speed drive gear 23 a and the fifth-speeddrive gear 25 a. When the first primary shaft 11 and the third-speeddrive gear 23 a rotate together, the sun gear 32 mounted on the firstprimary shaft 11 and the carrier 36 connected to the third-speed drivegear 23 a via the connecting shaft 13 rotate together, and the ring gear35 also rotate together with them, whereby the planetary gear mechanism30 becomes integral.

A first idler driven gear 27 b is mounted integrally on the firstintermediate shaft 15, and this first idler driven gear 27 b meshes withthe idler drive gear 27 a mounted on the second primary shaft 12.

A second idler driven gear 27 c is mounted integrally on the secondintermediate shaft 16, and this second idler driven gear 27 c mesheswith the first idler driven gear 27 b mounted on the first intermediateshaft 15. The second idler drive gear 27 c makes up a first idler geartrain 27A together with the idler drive gear 27 a and the first idlerdriven gear 27 b. In addition, a second-speed drive gear 22 a and afourth-speed drive gear 24 a are provided on the second intermediateshaft 16 so as to rotate relative to the second intermediate shaft 16 inpositions which correspond to the third-speed drive gear 23 a and thefifth-speed drive gear 25 a, respectively, which are provided around thefirst primary shaft 11. A second speed changing shifter 52 is providedon the second intermediate shaft 16 between the second-speed drive gear22 a and the fourth-speed drive gear 24 a so as to connect or disconnectthe second intermediate shaft 16 and the second-speed drive gear 22 a orthe fourth-speed drive gear 24 a. When the second speed changing shifter52 is shifted in a second-speed connecting position, the secondintermediate shaft 16 and the second-speed drive gear 22 a rotatetogether. When the second speed changing shifter 52 is shifted in afourth-speed connecting position, the second intermediate shaft 16 andthe fourth-speed drive gear 24 a rotate together. When the second speedchanging shifter 52 is in a neutral position, the second intermediateshaft 16 rotates relative to the second-speed drive gear 22 a and thefourth-speed drive gear 24 a.

A first common driven gear 23 b, a second common driven gear 24 b, aparking gear 21, and a final gear 26 a are mounted on the counter shaft14 integrally and sequentially in that order from an opposite side to aside facing the engine 6.

Here, the first common driven gear 23 b meshes with the third-speeddrive gear 23 a mounted on the connecting shaft 13 and makes up athird-speed gear pair 23 together with the third-speed drive gear 23 a.The first common driven gear 23 b also meshes with the second-speeddrive gear 22 a mounted on the second intermediate shaft 16 and makes upa second-speed gear pair 22 together with the second-speed drive gear 22a.

The second common driven gear 24 b meshes with the fifth-speed drivegear 25 a mounted on the first primary shaft 11 and makes up afifth-speed gear pair 25 together with the fifth-speed drive gear 25 a.The second common driven gear 24 b also meshes with the fourth-speeddrive gear 24 a mounted on the second intermediate shaft 16 and makes upa fourth-speed gear pair 24 together with the fourth-speed drive gear 24a.

The final gear 26 a meshes with the differential gear mechanism 8, andthe differential gear mechanism 8 is connected to the driving wheels DW,DW via the drive shafts 9, 9. Consequently, power transmitted to thecounter shaft 14 is outputted from the final gear 26 a to thedifferential gear mechanism 8, the drive shafts 9, 9, and the drivingwheels DW, DW.

A third idler driven gear 27 d is mounted integrally on the reverseshaft 17, and this third idler driven gear 27 d meshes with the firstidler driven gear 27 b mounted on the first intermediate shaft 15. Thethird idler drive gear 27 d makes up a second idler gear train 27Btogether with the idler drive gear 27 a and the first idler driven gear27 b. A reverse drive gear 28 a, which meshes with the reverse drivengear 28 b mounted on the first primary shaft 11, is provided on thereverse shaft 17 so as to rotate freely relative to the reverse shaft17. The reverse drive gear 28 a makes up a reverse gear train 28together with the reverse driven gear 28 b. A reverse shifter 53 isprovided at an opposite side of the reverse drive gear 28 a to a sidefacing the engine 6, and this reverse shifter 53 connects or disconnectsthe reverse shaft 17 and the reverse drive gear 28 a. When the reverseshifter 53 is shifted in a reverse connecting position, the reverseshaft 17 and the reverse drive gear 28 a rotate together, and when thereverse shifter 53 is in a neutral position, the reverse shaft 17 andthe reverse drive gear 28 a rotate relative to each other.

The first speed changing shifter 51, the second speed changing shifter52 and the reverse shifter 53 employ a clutch mechanism with asynchromesh mechanism (a synchronizer mechanism) which makes relationspeeds of a shaft and a gear which are connected together coincide witheach other.

In the transmission 20 configured in the way described heretofore, anodd numbered speed gear group (a first gear group) made up of thethird-speed drive gear 23 a and the fifth-speed drive gear 25 a isprovided on the first primary shaft 11, which is one speed changingshaft of the two speed changing shafts, and an even numbered speed geargroup (a second gear group) made up of the second-speed drive gear 22 aand the fourth-speed drive gear 24 a is provided on the secondintermediate shaft 16, which is the other speed changing shaft of thetwo speed changing shafts.

The vehicle drive apparatus 1 includes further an air conditionercompressor 112 and an oil pump 122. The oil pump 122 is mounted on anoil pump accessory shaft 19 which is disposed parallel to the rotationalaxes A1 to E1 so as to rotate together with the oil pump accessory shaft19. An oil pump driven gear 28 c, which meshes with the reverse drivegear 28 a, and an air conditioner drive gear 29 a are mounted on the oilpump accessory shaft 19 so as to rotate together therewith, whereby thepower of the engine 6 and/or the motor 7 which rotates the first primaryshaft 11 is transmitted to the oil pump accessory shaft 19.

The air conditioner compressor 112 is provided on an air conditioneraccessory shaft 18 which is disposed parallel to the rotational axes A1to E1 via an air conditioner clutch 121. An air conditioner driven gear29 b, to which the power is transmitted from the air conditioner drivegear 29 a via a chain 29 c, is mounted on the air conditioner accessoryshaft 18 so as to rotate together with the air conditioner accessoryshaft 18, whereby the power of the engine 6 and/or the motor 7 istransmitted from the oil pump accessory shaft 19 to the air conditioneraccessory shaft 18 via an air conditioner transmission mechanism 29 madeup of the air conditioner drive gear 29 a, the chain 29 c and the airconditioner driven gear 29 b. The transmission of the power to the airconditioner compressor 112 can be cut off by engaging and disengagingthe air conditioner clutch 121 by an air conditioner solenoid, notshown.

Being configured in the way described heretofore, the hybrid electricvehicle drive apparatus 1 of this embodiment has the following first tofifth transmission lines.

-   (1) A first transmission line is a transmission line in which the    crankshaft 6 a of the engine 6 is connected to the driving wheels    DW, DW by way of the first primary shaft 11, the planetary gear    mechanism 30, the connecting shaft 13, the third-speed gear pair 23    (the third-speed drive gear 23 a, the first common driven gear 23    b), the counter shaft 14, the final gear 26 a, the differential    mechanism 8 and the drive shafts 9, 9. Here, a speed reduction ratio    of the planetary gear mechanism 30 is set so that engine torque    transmitted to the driving wheels DW, DW by way of the first    transmission line corresponds to a first speed. Namely, a speed    reduction ratio resulting from multiplying the speed reduction ratio    of the planetary gear mechanism 30 by a speed reduction gear ratio    of the third-speed gear pair 23 corresponds to the first speed.-   (2) A second transmission line is a transmission line in which the    crankshaft 6 a of the engine 6 is connected to the driving wheels    DW, DW by way of the second primary shaft 12, the first idler gear    train 27A (the idler drive gear 27 a, the first idler driven gear 27    b, the second idler driven gear 27 c), the second intermediate shaft    16, the second-speed gear pair 22 (the second-speed drive gear 22 a,    the first common driven gear 23 b) or the fourth-speed gear pair 24    (the fourth-speed drive gear 24 a, the second common driven gear 24    b), the counter shaft 14, the final gear 26 a, the differential    mechanism 8, and the drive shafts 9, 9.-   (3) A third transmission line is a transmission line in which the    crankshaft 6 a of the engine 6 is connected to the driving wheels    DW, DW by way of the first primary shaft 11, the third-speed gear    pair 23 (the third-speed drive gear 23 a, the first common driven    gear 23 b) or the fifth-speed gear pair 25 (the fifth-speed drive    gear 25 a, the second common driven gear 24 b), the counter shaft    14, the final gear 26 a, the differential mechanism 8 and the drive    shafts 9, 9 without involving the planetary gear mechanism 30 in the    transmission line.-   (4) A fourth transmission line is a transmission line in which the    motor 7 is connected to the driving wheels DW, DW by way of the    planetary gear mechanism 30 or the third-speed gear pair 23 (the    third-speed drive gear 23 a, the first common driven gear 23 b) or    the fifth-speed gear pair 25 (the fifth-speed drive gear 25 a, the    second common driven gear 24 b), the counter shaft 14, the final    gear 26 a. the differential mechanism 8 and the drive shafts 9, 9.-   (5) A fifth transmission line is a transmission tine in which the    crankshaft 6 a of the engine 6 is connected to the driving wheels    DW, DW by way of the second primary shaft 12, the second idler gear    train 27B (the idler drive gear 27 a, the first idler driven gear 27    b, the third idler driven gear 27 d), the reverse shaft 17, the    reverse gear train 28 (the reverse drive gear 28 a, the reverse    driven gear 28 b), the planetary gear mechanism 30, the connecting    shaft 13, the third-speed gear pair 23 (the third-speed drive gear    23 a, the first common driven gear 23 b), the counter shaft 14, the    final gear 26 a, the differential mechanism 8, and the drive shafts    9, 9.

Additionally, as shown in FIG. 2, in the hybrid electric vehicle driveapparatus 1 of this embodiment, the motor 7 is connected to a powerdrive unit (hereinafter, referred to as PDU) 2 which controls theoperation thereof. The PDU 2 is connected to the battery 3 whichsupplies electric power to the motor 7 or which is charged with electricpower from the motor 7. The motor 7 is driven by electric power suppliedthereto from the battery 3 by way of the PDU 2. The motor 7 can performa regenerative generation by employing the rotation of the drivingwheels DW, DW while the hybrid electric vehicle is being decelerated orthe power of the engine 6 to charge (to recover the energy to) thebattery 3. Further, the PDU 2 is connected to an electronic control unit(hereinafter, referred to ECU) 5. The ECU 5 is a control unit whichgoverns various controls of the whole of the hybrid electric vehicle andis connected to a gradient sensor 55 for detecting a gradient of a roadsurface on which the hybrid electric vehicle is being driven and avehicle speed sensor 56 for detecting a current vehicle speed.

The results of a detection executed by the vehicle speed sensor 56 areinputted into the ECU 5. Additionally, inputted into the ECU 5 aresignals which signal an accelerator pedal position degree indicating anacceleration requirement, brake pedal effort indicating a brakerequirement, an engine speed, a motor speed, rotation speeds of thefirst and second primary shafts 11, 12, a rotation speed of the countershaft 14, a vehicle speed, a speed gear and a shift position. On theother hand, outputted from the ECU 5 are a signal controlling the engine6, a signal controlling the PDU 2, a signal controlling the motor 7,signals signalling a generating state, a charging slate and adischarging state of the battery 3, signals controlling the first andsecond speed changing shifters 51, 52 and the reverse shifter 53, asignal controlling the engagement (lock) and disengagement (neutral) ofthe synchromesh mechanism 61 and a signal controlling the engagement anddisengagement of the air conditioner clutch 121.

In addition, as shown in FIG. 3, the ECU 5 has an accelerator pedalposition degree determining portion 81 for determining an acceleratorpedal position degree based on an inputted signal signalling anaccelerator pedal position degree, a starting torque denying portion 82for deriving a torque to be outputted from the motor 7 to start theengine 6, a maximum torque deriving portion 83 for deriving a maximumtorque that the motor 7 can output, a torque limit value setting portion84 for setting a torque to be outputted from the motor 7 for an EVdriving in which the hybrid electric vehicle is driven only by the powerof the motor 7, a vehicle speed determining portion 85 for determiningon a vehicle speed based on an input from a vehicle speed sensor 56, abattery state determining portion 86 for detecting a state of thebattery 3 such as a stale of charge (SOC) or temperature thereof, amaximum energy amount deriving portion 87 a for deriving a maximumenergy amount that the battery 3 can output based on the stale of thebattery 3, and a maximum energy amount determining portion 87 b fordetermining on a maximum energy amount.

With the hybrid electric vehicle drive apparatus 1 which is configuredin the way described above, first- to fifth-speed drivings or forwarddrivings with the first- to fifth-speed gears and a reverse driving canbe performed by the engine 6 by controlling the engagement anddisengagement of the first and second clutches 41, 42 and controllingthe connecting positions of the first speed changing shifter 51, thesecond speed changing shifter 52 and the reverse shifter 53.

In the first-speed driving, the driving force is transmuted to thedriving wheels DW, DW by way of the first transmission line by engagingthe first clutch 41 and connecting the synchromesh mechanism 61. In thesecond-speed driving, the driving force is transmitted to the drivingwheels DW, DW by way of the second transmission line by engaging thesecond clutch 42 and shifting the second speed changing shifter 52 inthe second-speed connecting position, and in the third-speed driving,the driving force is transmitted to the driving wheels DW, DW by way ofthe third transmission line by engaging the first clutch 41 and shiftingthe first speed changing shifter 51 in the third-speed connectingposition.

In the fourth-speed driving, the driving force is transmitted to thedriving wheels DW, DW by way of the second transmission line by shiftingthe second speed changing shifter 52 in the fourth-speed connectingposition, and in the fifth-speed driving, the driving force istransmitted to the driving wheels DW, DW by way of the secondtransmission line by shifting the first speed changing shifter 51 in thefifth-speed connecting position. Further, the reverse driving isperformed by way of the fifth transmission line by engaging the secondclutch 42 and connecting the reverse shifter 53.

The motor 7 is allowed to assist the engine 6 in driving the hybridelectric vehicle by connecting the synchromesh mechanism 61 while thehybrid electric vehicle is being driven by the engine 6 or pre-shiftingthe first and second speed changing shifters 51, 52. Further, the motor7 is allowed to start the engine 6 or charge the battery 3 even duringidling. Further, the EV driving can also be effected by the motor 7 bydisengaging the first and second clutches 41, 42.

As driving modes of the EV driving, there are a first-speed EV drivingmode in which the hybrid electric vehicle is driven by way of the fourthtransmission line by disengaging the first and second clutches 41, 42and connecting the synchromesh mechanism 61, a third-speed EV drivingmode in which the hybrid electric vehicle is driven by way of the fourthtransmission line by shifting the first speed changing shifter 51 in thethird-speed connecting position, and a fifth-speed EV driving in whichthe hybrid electric vehicle is driven by way of the fourth powertransmission line by shifting the first speed changing shifter 51 in thefifth-speed connecting position.

Here, as an example of the EV driving, referring to FIGS. 4A and 4B, thefirst-speed EV driving mode (the 1st EV driving mode) will be described.

The 1st EV driving mode is effected by shifting the synchromeshmechanism 61 from an initial state to a lock state (the lock of OWC isON). In this state, when the motor 7 is driven (torque is applied in aforward rotating direction), as shown in FIG. 4A, the sun gear 32 of theplanetary gear mechanism 31 connected to the rotor 72 rotates in theforward rotating direction. As this occurs, as shown in FIG. 4B, sincethe first and second clutches 41, 42 are disengaged, the powertransmitted to the sun gear 32 is never transmitted to the crankshaft 6a of the engine 6 from the first primary shaft 11. Then, since thesynchromesh mechanism 61 is locked, the motor torque is transmitted fromthe sun gear 32 to the carrier 36 while being decelerated and istransmitted to the driving wheels DW, DW by way of the fourthtransmission line which passes through the third-speed gear pair 23.

In a reverse driving in the 1st EV driving mode, the motor 7 is drivenin a reverse rotating direction, whereby the motor torque can be appliedin the reverse totaling direction.

When the hybrid electric vehicle is driven in the EV driving mode, themaximum torque that the motor 7 can output, that is, the maximum drivingforce of the motor 7 differs depending upon the speed gear used fordriving or the vehicle speed. FIG. 5 is a graph showing a relationshipbetween the driving force of the motor and the engine or the rotationspeed of the crankshaft of the engine and the vehicle speed in eachspeed gear. In FIG. 5, three lines indicated by a thin solid line Adenote maximum driving forces that the motor 7 can output when thehybrid electric vehicle is driven in the first-speed EV driving mode,the third-speed EV driving mode and the filth-speed EV driving mode,respectively.

Incidentally, in the event of the engine 6 being started when the hybridelectric vehicle is being driven in the first-speed EV driving mode, thefirst primary shaft 11 is connected directly to the crankshaft 6 a ofthe engine 6 by connecting the first clutch 41, for example. Therefore,the torque is transmitted from the first primary shaft 11 to thecrankshaft 6 a of the engine 6 to thereby crank the crankshaft 6 a,whereby the engine 6 can be started in the first speed.

In this case, since the engine 6 is started while the hybrid electricvehicle continues to be driven, the torque outputted by the motor 7 istransmitted to both the counter shall 14 and the first primary shaft 11.Because of this, in case the torque outputted by the motor 7 when theengine is started remains equal to the torque with which the hybridelectric vehicle is driven in the first-speed EV driving mode, thetorque transmitted to the driving wheels DW, DW by way of the countershaft 14 is reduced, resulting in fears that a shock is produced. Then,normally, in starting the engine 6 while the hybrid electric vehicle isbeing driven in the EV driving mode, the motor 7 is controlled so as tooutput an amount of torque (starting torque) equal to the torquetransmitted to the engine 6, so that the engine 6 can smoothly bestarted without producing any shock.

Because of this, normally, when the hybrid electric vehicle is driven inthe EV driving mode, the torque of the motor 7 which is used as thedriving force is limited so as to leave extra torque as torque to startthe engine 6 for preparation for starting the engine 6 in the future.Consequently, the torque that the motor 7 outputs when driving thehybrid electric vehicle in the EV driving mode is not the maximum torquethat the motor 7 can output but the torque which is limited by a value(a torque limit value) which results from subtracting the startingtorque to start the engine 6 from the maximum torque.

In FIG. 5, three lines indicated by a thin broken line B denote limitvalues for driving forces which are outputted by the motor 7 as drivingforces for driving the hybrid electric vehicle when the hybrid electricvehicle is driven in the first-speed EV driving mode, the third-speed EVdriving mode and the fifth-speed EV driving mode, respectively. Namely,the driving force that the motor 7 can output in driving the hybridelectric vehicle in the first EV driving mode is not the maximum drivingforce (indicated by the “1st” thin solid line A) that the motor 7 canoriginally output but is the driving force limited by a driving forcelimit value (indicated by the “1st” thin broken line B) by which thedriving force is limited to a driving force resulting from removing thedriving force used to start the engine 6. In this way, in driving thehybrid electric vehicle in the EV driving mode, the PDU 2 and the motor7 are normally controlled by the ECU 5 so that the output torque of themotor 7 falls within the scope of the torque limit value.

In FIG. 5, five lines indicated by a thick solid line C denoterelationships between the vehicle speed and the rotation speed of thecrankshaft of the engine 6 when the hybrid electric vehicle is enginedriven in the first to fifth speeds, respectively. Five lines indicatedby a thick broken line D denote maximum driving forces that the engine 6can output in driving the hybrid electric vehicle in the first to fifthspeeds, respectively. Five lines indicated by a thick alternate long andshort dash line E denote totals of maximum driving forces that theengine 6 and the motor 7 can output in driving the hybrid electricvehicle using the driving forces of both the engine 6 and the motor 7 inthe first to fifth speeds, respectively.

Incidentally, in driving the hybrid electric vehicle on a slope with anupward gradient, the running resistance increases according to thegradient, and therefore, the driver depresses the accelerator pedal moreas the driving force required increases greater. In the event of thehybrid electric vehicle being driven on a slope with an upward gradientin the first-speed EV driving mode as shown in FIGS. 4A and 4B, in casethe motor 7 is controlled so as to output torque which falls within thescope of the torque limit value as normal even though the acceleratorpedal is depressed more than when driving the hybrid electric vehiclenormally on a flat road, there are fears that a sufficient speed oracceleration cannot be obtained. Although it is desirable that apredetermined vehicle speed according to the speed gear used whenstarting the engine 6 is reached in starting the engine 6 while thehybrid electric vehicle is being driven in the EV driving mode, in casethe output torque of the motor 7 is controlled within the scope of thetorque limit value, a sufficient acceleration cannot be obtained, andtherefore, there is the possibility that it may take some time beforethe predetermined vehicle speed is reached.

Then, in this embodiment, in the event that the vehicle speed is notincreased although the accelerator pedal position degree is controlledto increase the vehicle speed, the torque limit value is modified. Whilethe hybrid electric vehicle is being driven on a flat road, the torquelimit value setting portion 84 sets the torque limit value to a firsttorque limit value To which is derived by subtracting a sufficientstarting torque from the maximum torque. As this occurs, the ECU 5controls the PDU 2 and the motor 7 so that the torque outputted by themotor 7 falls within the scope of the first torque limit value To. Thesufficient starting torque means torque which is greater than a minimumtorque which is necessary for the motor 7 to start the engine 6 which isbeing stopped.

However, when the vehicle speed is not increased even though theaccelerator pedal is depressed while the hybrid electric vehicle isbeing driven on a slope with an upward gradient, in case the ECU 5controls the motor 7 within the scope of the first torque limit valueTo, there are fears that a sufficient speed or acceleration cannot beobtained. Then, when the vehicle speed is not increased even though theaccelerator pedal is depressed, allowing the accelerator pedal positiondegree to reach a threshold, in case the vehicle speed is not stillincreased even after the passage of a predetermined length of time, thetorque limit value setting portion 84 sets the torque limit value to asecond torque limit value Ts which is greater than the first torquelimit value To. The second torque limit value Ts is set so as to begreater than the first torque limit value To within the scope of themaximum torque that the motor 7 can output. The second torque limitvalue Ts is set so that a difference between the second torque limitvalue Ts and the maximum torque becomes the minimum torque necessary forthe motor 7 to start the engine 6. As this occurs, the ECU 5 controlsthe PDU 2 and the motor 7 so that the torque outputted by the motor 7falls within the scope of the second torque limit value Ts. By adoptingthis configuration, when the accelerator pedal is depressed while thehybrid electric vehicle is being EV driven on a slope with an upwardgradient, since the hybrid electric vehicle can be driven with a greaterdriving force, a desired speed and acceleration can be obtained.

In case the hybrid electric vehicle which is being driven at low vehiclespeeds reaches or exceeds a lower limit vehicle speed at which the firstclutch 41 which is connected to the engine 6 can be engaged, the ECU 5may control the motor 7 so as to output the starting toque in additionto the driving torque to thereby start the engine 6. As this occurs, theECU 5 raises the engaging torque with which the first crutch 41 isengaged as the starting torque of the motor 7 is raised, so as to raisethe revolution speed of the engine 6. When the revolution speed of theengine 6 reaches or exceeds a revolution speed at which the engine 6 canoperate alone without any assistance of the motor 7, fuel is started tobe supplied to the engine 6 and the engine 6 is ignited to start itsoperation. However, after the engine 6 is started, the torque limitvalue setting portion 84 of the ECU 5 sets the torque limit value to thefirst torque limit value To.

In the event that a maximum energy amount E that the battery 3 canoutput becomes less than a predetermined value Eth while the hybridelectric vehicle is being EV driven, the ECU 5 controls the engine 6 soas to be started. The maximum energy amount E that the battery 3 canoutput is derived by the maximum energy amount deriving portion 87 abased on the SOC or temperature of the battery 3 which is detected bythe battery state detecting portion 86. Then, the maximum energy amountdetermining portion 87 b determines whether or not the maximum energyamount E is less than the predetermined value Eth. The EV driving iseffected by driving the motor 7 with the energy outputted from thebattery 3. In the event of the maximum energy amount E<Eth, it isdetermined that it is difficult to obtain sufficient energy to allow theEV driving mode to continue from the battery 3. Then, as this occurs,the engine 6 is controlled to be started so that the driving force canbe outputted by the engine 6. The predetermined value Eth can bedetermined based on the speed gear currently used. Additionally, thepredetermined value Eth may be determined according to the gradient of aroad surface on which the hybrid electric vehicle is being driven.

In the event that the vehicle speed V detected by the vehicle speedsensor 56 reaches or exceeds a predetermined value Vth, the engine 6 iscontrolled be started. In the event that the vehicle speed V is equal toor faster than the predetermined value Vth, it is determined that therequired driving force is high and that the driver's intention toaccelerate the hybrid electric vehicle is high, and therefore, it isdetermined that it is difficult to continue the EV driving mode. Then,in the event that the vehicle speed determining portion 85 determinesthat the vehicle speed V≧Vth, the engine 6 is controlled to be startedso that the driving force can be outputted by the engine 6. Thepredetermined value Vth can be determined based on the speed gearcurrently used. Additionally, the predetermined value Vth may bedetermined according to the gradient of a road surface on which thehybrid electric vehicle is being driven.

After the engine 6 is started, the hybrid electric vehicle may be drivenin an assist driving mode in which both the engine 6 and the motor 7output the driving forces or may be driven in an engine driving mode inwhich only the engine 6 outputs the driving force by stopping the supplyof energy from the battery 3 to the motor 7. In addition, the motor 7may perform a regenerative generation by using the power of the engine 6so as to charge (to recover the energy to) the battery 3.

In starting the engine 6 when the hybrid electric vehicle is beingdriven in the first-speed EV driving mode, the engine 6 can be startedin the first speed by engaging the first clutch 41 as has been describedabove. In addition to this, the engine 6 can also be started in thesecond speed by first shifting the second speed changing shifter 52 inthe second-speed connecting position while the hybrid electric vehicleis being driven in the first-speed EV driving mode and thereafterengaging the second clutch 42. In this way, in case the engine 6 can bestarted in a higher speed gear than the currently used speed gear, thetorque necessary to start the engine 6 can be reduced. As is seen fromthe five thick solid lines C in FIG. 5, when comparing them at pointswhere the revolution speed of the crankshaft 6 a of the engine 6 becomethe same, the vehicle speed required when starting the engine 6 becomesfaster as the speed gears become higher. However, according to thisembodiment, in the event that the vehicle speed is not increasedalthough the accelerator pedal is depressed, since the motor 7 islimited within the scope of the second torque limit value Ts which isgreater than the first torque limit value To which is normal, the highervehicle speed can be reached earlier. Thus, the engine can be started inthe second speed while the hybrid electric vehicle is being driven inthe 1st EV driving mode.

Hereinafter, a state in which the second speed changing shifter 52 ispre-shifted in the second speed connecting position while the hybridelectric vehicle is being driven in the first-speed EV driving mode willbe referred to as a 1st EV driving Pre2 mode. FIGS. 6A and 6B show atorque transmission during the 1st EV driving Pre2 mode. Although thetorque transmission in the 1st EV driving Pre2 mode is similar to thatof the 1st EV driving mode shown in FIGS. 4A and 4B, here, as a resultof the second speed changing shifter 52 having been shifted in thesecond speed connecting position, the second speed drive gear 22 a andthe second intermediate shaft 16 rotate together. As a result of thesecond intermediate shaft 16 rotating, the second primary shaft 12rotates from the second idler driven gear 27 c mounted on the secondintermediate shaft 16 by way of the first idler driven gear 27 b and theidler drive gear 27 a.

By engaging the second clutch 42 from this state, the second primaryshaft 12 is connected directly to the crankshaft 6 a of the engine 6,whereby the crankshaft 6 a is cranked. Hereinafter, a state will bereferred to as a 1st EV driving mode 2nd engine start in which thesecond clinch 42 is engaged with the second speed changing shifter 52shifted in the second speed connecting position, so that the crankshaft6 a is cranked by way of the second intermediate shaft 16 and the secondprimary shaft 12 while the hybrid electric vehicle is being driven inthe first speed EV driving mode. FIGS. 7A and 7B show a torquetransmission during the 1st EV driving mode 2nd engine start. It is seenfrom FIGS. 7A and 7B that the torque outputted by the motor 7 istransmitted not only to the counter shaft 14 but also to the crankshaft6 a of the engine 6. In this way, the torque necessary to crank theengine 6 can be reduced by starting the engine 6 in the second speedwhile the hybrid electric vehicle is being driven in the 1st EV drivingmode, whereby it is possible to reduce the influence imposed on thedriving wheels DW, DW.

FIG. 8 is a timing chart showing an example of a change in eachparameter while the hybrid electric vehicle is being EV driven on anascending path. Unless the vehicle speed is increased although theaccelerator pedal is depressed so that the accelerator pedal positiondegree (AP position degree) is controlled to increase the vehicle speedas indicated by a broken line as shown in (a) of FIG. 8, unless thevehicle speed is increased although the accelerator pedal reaches afirst threshold (an AP position degree Hi) at a point in time of a timet1 and unless the vehicle speed is increased although a counter valueshown in (b) FIG. 8 which is measured by being counted up from thatpoint in time reaches a threshold at a point in time of a time t2, atorque limit value change flag is set as shown in (c) of FIG. 8, so thatthe torque limit value of the motor 7 is set to the second torque limitvalue Ts. Thereafter, as shown in (d) of FIG. 8, the vehicle speedincreases because the torque of the motor 7 is outputted which exceedsthe first torque limit value, and the driver mitigates the pedal effortexerted on the accelerator pedal. As this occurs, in case theaccelerator pedal position degree is lowered to the first threshold (theAP position degree Hi) at a point in time of a time t3, the torque limitvalue setting portion 84 of the ECU 5 reduces gradually the torque limitvalue from the second torque limit value Ts. The torque limit valuesetting portion 84 reduces the torque limit value step by step as theaccelerator pedal position degree is lowered. Thereafter, in case theaccelerator pedal position degree is lowered to a second threshold (anAP position degree Lo) at a point in time of a time t4, the torque limitsetting portion 84 sets the torque limit value to the first torque limitvalue To.

Different values are set for the threshold of the counter value shown in(b) of FIG. 8 according to the vehicle speed as shown in FIG. 9.

As has been described heretofore, according to the hybrid electricvehicle drive apparatus 1 of this embodiment, in the event that thevehicle speed is not increased although the accelerator pedal positiondegree is controlled to increase the vehicle speed while the hybridelectric vehicle is being driven in the EV driving mode, in order toraise the limit value of the output torque of the motor 7, theacceleration or the vehicle speed according to the requirement from thedriver is maintained while keeping the hybrid electric vehicle driven inthe EV driving mode, thereby making it possible to hold the drivingperformance of the hybrid electric vehicle. In this way, since thecontrol is changed according to the requirement of the driver, thecontrol can be effected which is based on the behavior of the hybridelectric vehicle that have actually been sensed by the driver.

The invention is not limited to the embodiment that has been describedheretofore and hence can be modified or improved as required.

For example, in the hybrid electric vehicle drive apparatus 1, the oddnumbered speed gears are disposed on the first primary shaft 11 which isthe input shaft to which the motor 7 of the twin clutch typetransmission is connected, while the even numbered speed gears aredisposed on the second intermediate shaft 16 which is the input shaft towhich the motor 7 is not connected. However, the invention is notlimited thereto, and hence, a configuration may be adopted in which theeven numbered speed gears are disposed on the first primary shaft 11which is the input shaft to which the motor 7 is connected, while theodd numbered speed gears are disposed on the second intermediate shaft16 which is the input shaft to which the motor 7 is not connected.

A seventh, ninth and further speed gears may be provided in addition tothe planetary gear mechanism 30 as the first-speed drive gear, thethird-speed drive gear 23 a and the fifth-speed drive gear 25 a as oddnumbered speed gears, and as even numbered speed gears, a sixth, eighthand further speed gears may be provided in addition to the second-speeddrive gear 22 a and the fourth-speed drive gear 24 a. In addition, thegradient S may be derived in consideration of the payload of the hybridelectric vehicle.

While the invention has been described in detail and by reference to thespecific embodiment, it is obvious to those skilled in the art to whichthe invention pertains that various alterations or modifications can bemade thereto without departing from the spirit and scope of theinvention.

This patent application is based on the Japanese Potent Application (No.2013-183531) filed on Sep. 4, 2015, the contents of which areincorporated herein by reference.

DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS

-   1 hybrid electric vehicle drive apparatus-   3 battery (battery)-   5 ECU-   6 engine (internal combustion engine)-   7 motor (electric motor)-   11 first primary shaft (first input shaft)-   14 counter shaft (output shaft)-   16 second intermediate shaft (second input shaft)-   1 first clutch (first engaging and disengaging portion)-   42 second clutch (second engaging am) disengaging portion)-   51 first speed changing shifter-   52 second speed changing shifter-   20 transmission-   81 accelerator pedal position degree determining portion-   82 starting torque deriving portion-   83 maximum torque deriving portion-   84 torque limit value setting portion-   85 vehicle speed determining portion-   86 battery state detecting portion-   87 a maximum energy amount deriving portion-   87 b maximum energy, amount determining portion

The invention claimed is:
 1. A hybrid electric vehicle drive apparatusincluding an internal combustion engine, a transmission having two ormore input shafts, an electric motor which is connected to either of theinput shafts of the transmission so as to transmit power thereto, and anengaging and disengaging portion which engages and disengages theinternal combustion engine and the transmission, and configured to bedriven by power of at least one of the internal combustion engine andthe electric motor, comprising: a maximum torque deriving portion forderiving a maximum torque that the electric motor enables to output; astarting torque deriving portion for deriving a starting torque for usein starting the internal combustion engine by the electric motor; atorque limit value setting portion for setting a limit value of adriving torque that the electric motor outputs when the vehicle driveswith power of the electric motor only, based on the maximum torque andthe starting torque; a vehicle speed acquiring portion for acquiring aspeed of the vehicle; and an accelerator pedal position degree acquiringportion for acquiring a position degree of an accelerator pedal, whereinthe torque limit value setting portion sets the limit value of thedriving torque to a first driving torque value and sets the limit valueof the driving torque to a second driving torque value which is greaterthan the first driving torque value when the speed does not increaseeven though the accelerator pedal position degree increases while thevehicle is being driven only by the electric motor.
 2. The hybridelectric vehicle drive apparatus according to claim 1, wherein thetorque limit value setting portion sets the limit value of the drivingtorque to the second driving torque value which is greater than thefirst driving torque value when the vehicle speed does not continue toincrease over a predetermined length of time or more even though theaccelerator pedal position degree increases.
 3. The hybrid electricvehicle drive apparatus according to claim 1, wherein the torque limitvalue setting portion reduces the limit value of the driving torque fromthe second driving torque value in a case that the accelerator pedalposition degree is lowered with the limit value of the driving torqueset to the second driving torque value.
 4. The hybrid electric vehicledrive apparatus according to claim 3, wherein the torque limit valuesetting portion reduces the limit value of the driving torque step bystep as the accelerator pedal position degree is lowered when the torquelimit value setting portion reduces the limit value of the drivingtorque from the second driving torque value to the first driving torquevalue.
 5. The hybrid electric vehicle drive apparatus according to claim1, wherein when the vehicle speed is equal to or greater than apredetermined vehicle speed, the electric motor outputs the startingtorque in addition to the driving torque to start the internalcombustion engine.
 6. The hybrid electric vehicle drive apparatusaccording to claim 5, wherein the torque limit value setting portionsets the limit value of the driving torque to the first driving torquevalue after the internal combustion engine is started.
 7. The hybridelectric vehicle drive apparatus according to claim 1, wherein adifference between the second driving torque value and the maximumtorque is a minimum torque which is necessary for the electric motor tostart the internal combustion engine.